Recently, satellite broadcast techniques have remarkably been developed. The Japanese Laid-Open Patent Application No. 5-284506, "Multimedia Selector for Satellite Broadcasts," discloses a technique for providing multimedia information being composed of images, voices, and digital data by superposing selectable pieces of digital data on an analog image signal. For example, it is possible with this technique to superimpose a subtitle on a broadcast image, the subtitle being one out of a plurality of languages selected by the user and being provided as digital data. This enables users of a broadcast system to select desired information among information transmitted to the users in one direction by the broadcast system. In other words, user interfaces are achieved as multimedia information transmission systems in which users can select desired information.
However, the above conventional technique discloses one video stream with one fixed user interface (digital data). Such a user interface may not be suited for all users. Also, it is impossible for program providers in the broadcast system to provide high-level, effective programs which are respectively arranged for different users since the system transmits only fixed user interfaces.